The present invention relates to heating devices for heat-sealing containers for use in folding end portions of tubular blanks having a square or rectangular cross section to a flat form which end portions are to be made into bottom portions or top portions of containers and heat-sealing the folded end portions.
Already known as such a device is a heating device for heating a bottom forming portion of a tubular container having a rectangular to square cross section, the bottom forming portion having four generally quadrilateral first to fourth bottom panels continuous with one another and each having a heating region to be heated on the inner surface thereof. The heating device has a hot air nozzle in the form of a bottomed tube and fittable into the container bottom forming portion for heating the inner surface of the container, the nozzle having four side walls continuous with one another and corresponding to the first to fourth bottom panels respectively, each of the side walls being provided with a hot air discharge portion having orifices and to be opposed to the heating region of the corresponding bottom panel and with a hot air nondischarge portion other than the discharge portion, the entire hot air discharge and nondischarge portions of each side wall being holdable at a specified spacing from the corresponding bottom panel. (See JP-A 11-240083).
The conventional device is adapted to heat the inner surface of each bottom panel concentrically over the heating region with hot air forced out from the orifices of the nozzle as opposed to the region. Although there arises no problem if only the heating region is heated, it is likely that the nonheating region other than the heating region will be heated, presumably for the following two reasons. First, the hot air forced out of the orifices is brought into contact not only with the heating region but also with the nonheating region adjacent thereto, permitting the nonheating region to become heated. Second, the hot air forced out of the orifices of the hot air discharge portion of the nozzle for the heating region will heat the hot air nondischarge portion having no orifices, with the result that the nonheating region becomes heated with the heat radiating from the heated nondischarge portion.
If the region which need not be heated is heated, this entails the possibility of causing damage to the packaging material. Since the bottom portion of the container is in contact with the liquid contents at all times especially during transport, the damage caused to the packaging material will result in faults such as a leak of contents.
An object of the present invention is to provide a heating device for heat-sealing containers which is useful for heat-sealing end portions of containers and which is adapted to concentrically heat required portions only of a packaging material to be made into the container.
The present invention provides a heating device for heat-sealing containers by heating an end forming portion of a tubular container having a rectangular to square cross section, the end forming portion having four generally quadrilateral first to fourth panels continuous with one another and each having a heating region to be heated on an inner surface thereof, the heating device having a hot air nozzle in the form of a bottomed tube and fittable into the container end forming portion for heating an inner surface of the container, the nozzle having four side walls continuous with one another and corresponding to the first to fourth panels respectively, at least one of the side walls being provided with a hot air discharge portion having orifices and to be opposed to the heating region of the corresponding panel and with a hot air nondischarge portion other than the discharge portion, the hot air nondischarge portion being at least partly provided with a hot air escape portion.
With the heating device of the invention, the hot air nondischarge portion, as positioned inside the panels, is at least partly provided with the hot air escape portion, so that hot air forced out from the hot air discharge portion flows through the hot air escape portion and is rapidly discharged from a space between the nondischarge portion and the panel opposed thereto. This eliminates the likelihood that the portion other than the heating region will be unnecessarily heated. Furthermore, even if the hot air nondischarge portion is heated with the hot air forced out from the discharge portion, the escape portion reduces the influence of the heat radiating from the heated nondischarge portion. Accordingly, the portion of the panel other than the heating region will not be heated but the heating region only can be heated concentrically.
If the hot air discharge portion and the hot air nondischarge portion are divided into upper and lower portions by a boundary, with the hot air escape portion provided over the entire area of the nondischarge portion, the heating region only can be heated more efficiently.
When the boundary is substantially inverted V-shaped by extending upward from opposite ends of a lower edge of the side wall, the hot air can be discharged efficiently through the hot air nondischarge portion.
The present invention provides another heating device for heat-sealing containers by heating an end forming portion of a tubular container having a rectangular to square cross section, the end forming portion having four generally quadrilateral first to fourth panels continuous with one another and each having a heating region to be heated on an outer surface thereof,
the heating device having a hot air nozzle to be fitted around the container end forming portion for heating an outer surface of the container, the nozzle having four side walls continuous with one another and corresponding to the first to fourth panels respectively, at least one of the side walls being provided with a hot air discharge portion having orifices and to be opposed to the heating region of the corresponding panel and with a hot air nondischarge portion other than the discharge portion, the hot air nondischarge portion being at least partly provided with a hot air escape portion.
The heating device described above and embodying the invention is adapted to heat the outer surfaces of the panels in the same manner as the inner surfaces thereof without heating the portions other than the heating regions of the panels, thus heating the heating regions only concentrically.
The hot air discharge portion and the hot air nondischarge portion are divided into upper and lower portions by a substantially horizontal straight boundary interconnecting lengthwise intermediate portions of opposite side edges of the side wall, and the hot air escape portion is provided over the entire area of the nondischarge portion. The heating region can then be heated concentrically more effectively with the hot air forced out from the discharge portion.
The heating region provided on the outer surface of at least one of the four panels is zero, and the side wall corresponding to said one panel is provided with the hot air nondischarge portion only, the hot air escape portion being provided over the entire area of the nondischarge portion. The panel wherein the heating region is zero is then in no way heated, while the hot air forced out from other side walls can be rapidly discharged from between the panel and the side wall via the escape portion.
When the hot air nozzle is suspended from a mount plate, with a hot air vent clearance formed between-the mount plate and at least one peripheral portion of the hot air nozzle, hot air is unlikely remain between the container inner surface heating nozzle and the container outer surface heating nozzle undesirably. The heating region can then be concentrically heated more effectively.
The present invention provides another heating device for heat-sealing containers by heating a top forming portion of a tubular container having a rectangular to square cross section, the top forming portion having four generally quadrilateral first to fourth top panels continuous with one another and divided by first to fourth scores into first to fourth roof panels and first to fourth seal panels respectively, each of the first and fourth seal panels having a heating region to be heated on an outer surface thereof,
the heating device having a hot air nozzle in the form of a bottomed tube and fittable into the container top forming portion for heating an inner surface of the container, the nozzle having four side walls continuous with one another and corresponding to the first to fourth seal panels respectively, at least one of the side walls being provided with a hot air discharge portion having orifices and to be opposed to the heating region of the corresponding seal panel and with a hot air nondischarge portion other than the discharge portion, the hot air nondischarge portion being at least partly provided with a hot air escape portion.
With the heating device of the invention described, the hot air nondischarge portion, as positioned inside the seal panels, is at least partly provided with the hot air escape portion, so that hot air forced out from the hot air discharge portion flows through the hot air escape portion and is rapidly discharged from a space between the nondischarge portion and the panel opposed thereto. This eliminates the likelihood that the portion other than the heating region will be unnecessarily heated. Furthermore, even if the hot air nondischarge portion is heated with the hot air forced out from the discharge portion, the escape portion reduces the influence of the heat radiating from the heated nondischarge portion. Accordingly, the portion of the seal panel other than the heating region will not be heated but the heating region only can be heated concentrically.
The nozzle has a bottom wall, and the hot air escape portion is a recessed portion extending from the side wall of the nozzle to the bottom wall. This prevents the froth produced when the container is filled with contents from adhering to the bottom wall. This obviates the likelihood that the froth, if adhering to the bottom wall, will clog up the nozzle.
When two hot air discharge portions are positioned respectively on opposite sides of one hot air nondischarge portion, with the hot air escape portion provided over the entire area of the nondischarge portion, the heating region only can be heated more efficiently.
When a hot air nozzle to be fitted around the container top forming portion is suspended from a mount plate for heating an outer surface of the container, with a hot air vent clearance formed between the mount plate and the hot air nozzle for heating the container outer surface, hot air is unlikely to remain between this nozzle and the container inner surface heating nozzle. This assures concentric heating of the heating region with an improved efficiency.